4th order bandpass NEED HELP!!!

[JRC 0]

i have a 96 s10 reg cab and in order to have a bigger system im forced to build a blow-thru. ive decided that my best option is to do a 4th order bandpass with the port coming through the back of my cab. i like the idea of having a single octo-port (just because i think they look effin b-a). ive done read just about everything you can find on the net and also talked to a few guys who have them....but everyone says something different....my question is how do you tune these things??? "golden ratio/theory"???

 

i plan on using 4 Lanzar Max Pro 15's (yes i know what your thinking) but they dont need a ton of space and power

Edited March 28, 2013 by JRC

[JRC 0]

right now i have a design drawn up and it would be roughly 8.5 cubes total sealed and 13.5 cubes total ported with a 10" octo-port thats 8 inches long

[Polish 9]

There is no golden rule really. It all depends on what you want. You calculate the tuning frequency the same as a ported box or just use WinIsd or a similar program. Basically you only take the cu/ft of the ported side into account for tuning. You also should make sure the woofers have a fairly high QTS or they won't work the best in a 4th order. Some say .50 or higher, my woofers are .49 and they do great. (Lanzar MAX10D)

 

As for ratios - the higher you go the peakier it will be. You are at about a 1.5 : 1 ratio right now, which will work but I would shoot for higher myself. It will work at that ratio but I like to get as much gain as possible. My box is about 2.6 : 1 for example and tuned to 45hz. The tuning sounds high if you're only used to standard ported boxes but that is how it works with bandpass boxes. The sealed portion allows for greater low end extension than a standard ported box. If you tune it extra low like many do with ported boxes (30-33hz) you'll not have much output past that.

 

Oh as for the port - I've read many people saying to shoot for 1/2 the cone area. I ended up at about that myself, but I was only going for roughly 14 sq/in of port per cu/ft of ported enclosure and it just so happened I was also at 1/2 the cone area.

Edited March 28, 2013 by Polish

[///M5 2,833]

If you aren't limited in the blow through size a standard ported box will yield better results. BP may require a few iterations to nail down.

[JRC 0]

ok thats what i originally thought but ive been told that thats backwards....and the Qts. for these 15's are .75

and ///m5 that was my first thought but cutting a giant gaping hole in the back of my cab isnt my first choice...hence the 4th order bp...cuz its just the port

Edited March 28, 2013 by JRC

[Polish 9]

At .75 you should be good to roll then. If possible design it so you can swap out the port. This way you can change tuning if your first setup doesn't give you the results you're after.

[JRC 0]

At .75 you should be good to roll then. If possible design it so you can swap out the port. This way you can change tuning if your first setup doesn't give you the results you're after.

^yessss def 

[JRC 0]

polish i just got done goin thru your whole build and i have to say great job that 4th order looks sweet....and the whole impedance thing had me goin lol

[///M5 2,833]

and ///m5 that was my first thought but cutting a giant gaping hole in the back of my cab isnt my first choice...hence the 4th order bp...cuz its just the port

And that is a very valid reason (about the only) to use a BP box. The rest has been covered, but to rehash there is no golden ratio just a frequency response that is determine, by the driver, the box, and the environment. The first two are easily modeled, the third is up to you. I look forward to seeing the build!

[Polish 9]

polish i just got done goin thru your whole build and i have to say great job that 4th order looks sweet....and the whole impedance thing had me goin lol

 

Thanks man, I appreciate it. I think my meter had a loose battery connection that day or something, it was driving me nuts. I got it all squared away though and it's banging like a hooker now

 

Good luck with the build, I am curious how those Max Pros do in a 4th order myself.

[JRC 0]

polish i just got done goin thru your whole build and i have to say great job that 4th order looks sweet....and the whole impedance thing had me goin lol

 

Thanks man, I appreciate it. I think my meter had a loose battery connection that day or something, it was driving me nuts. I got it all squared away though and it's banging like a hooker now

 

Good luck with the build, I am curious how those Max Pros do in a 4th order myself.

o i can imagine ill have build pics comin soon i just got a million things to do to the truck first( redo all my airride then tons of bodywork/sheetmetal then the system....i almost wish it wasnt bagged with 20's cuz the notch in the bed and larger tubs take up sooooo much room

[JRC 0]

got the doors started and got a vid and pics..comin soon

Edited March 29, 2013 by JRC